For manufacturing semiconductor devices, fine processing with lithography utilizing a photoresist composition has been conventionally used. The fine processing is a processing method including: forming a thin film of a photoresist composition on a substrate to be processed such as a silicon wafer; irradiating the substrate with active light such as ultraviolet through a mask pattern having a pattern of semiconductor device; performing development; and treating the substrate by etching with an obtained photoresist pattern as a protection film. In recent years, semiconductor devices tend to be more highly integrated, and a wavelength of active light used becomes shorter, such that from KrF excimer lasers (248 nm) to ArF excimer lasers (193 nm). Accordingly, the active light produces diffused reflections and standing waves from a substrate. To overcome such disadvantages, an anti-reflective coating (Bottom Anti-Reflective Coating, BARC) has been applied between photoresist and a substrate to be processed.
As resist patterns become finer in the future, resist films are required to be thinner to overcome resolution issues, or to avoid falling down of resist patterns after development. Thus, it is difficult for the resist pattern to have a film thickness sufficient to process the substrate. Accordingly, in addition to a resist pattern, a resist underlayer film formed between a resist and a semiconductor substrate to be processed is also required to serve as a mask when the substrate is processed. As a resist underlayer film to be used in such a process, there is required a resist underlayer film for lithography having a selection ratio for a dry etching rate close to that of the resist, having a selection ratio for a dry etching rate smaller than that of the resist, or having a selection ratio for a dry etching rate smaller than that of the semiconductor substrate, unlike conventional high etch rate resist underlayer films (having faster etching rates).
As a polymer for the resist underlayer film described above, the following are exemplified:
a resist underlayer film-forming composition using polyvinyl carbazole (see Patent Documents 1, 2, and 3);
a resist underlayer film-forming composition using a fluorene phenol novolac resin (see for example, Patent Document 4);
a resist underlayer film-forming composition using a fluorene naphthol novolac resin (see for example, Patent Document 5);
a resist underlayer film-forming composition including a resin having a repeating unit of fluorene phenol and aryl alkylene (see for example, Patent Documents 6 and 7); and
a novolac resin using phenylnaphthylamine and acetaldehyde (see Patent Document 8).